Single-Cycle Collective Communication Over a Shared Network Fabric

In the multicore era, on-chip network latency and throughput have a direct impact on system performance. A highly important class of communication flows traversing the network is collective, i.e., one-to-many and many-to-one. Scalable coherence protocols often leverage imprecise tracking to lower the overhead of directory storage, in turn leading to more collective communications on-chip. Routers with support for message forking/aggregation have been previously demonstrated, supporting such protocols. However, even with the fastest possible designs today (1-cycle routers), collective flows on a k x k mesh still incur delays proportional to k since all communication is across the entire chip.